To Mark Jones - Both of the glucose readings that you gave were low, especially the initial reading of 11 ( if that is correct, and the subsequent reading of 69. I would add insulinoma to the differential diagnosis. It certainly is worth repeating that test;after a 4-6 hour fast to see what the level is. No longer than 6 hours, though. I have seen many older, "skinny" ferrets, and I don't consider that a problem, and lethargy is tough to gauge in ferrets as they get older, because most of them tend to slow down a bit. But check that glucose again, and keep us posted. Bruce Williams [log in to unmask] [Posted in FML issue 1136]